1. Technical Field
The present disclosure relates to a surface mount package for a semiconductor integrated device, a related assembly and manufacturing process; in particular, the following discussion will make reference, without this implying any loss of generality, to a package for an accelerometer sensor, e.g., for automotive applications.
2. Description of the Related Art
As it is known, semiconductor devices usually comprise a package, e.g., of plastic or ceramic material, designed to encapsulate one or more dice of semiconductor material integrating corresponding micromechanical structures (e.g., MEMS sensing structures) and/or integrated circuits (e.g., ASIC circuits coupled to the sensing structures); the package is commonly made by means of molding techniques.
For example, FIG. 1 shows a semiconductor device, denoted with 1, including a surface mount package 2, of a type usually known as “gull-wing leaded package”.
Package 2 includes an encapsulation 3, made of a molding compound, e.g., of an epoxy resin material, encapsulating in a housing space contained therewithin one or more dice of the semiconductor device 1 (here not shown). A certain number of leads 4 (in FIG. 1 four leads per side are shown as an example), of a metallic material, are electrically connected to the die (or dice) within the encapsulation 3 and protrudes therefrom, so as to allow electrical connection to the outside environment, typically via soldering to a printed circuit board (PCB) of an external electronic apparatus.
Leads 4 are shaped as gull wings (thus the common name for the package type), and have, outside the encapsulation 3, a first substantially flat portion 4a, joined to the encapsulation 3, a second substantially flat portion 4b that is to be soldered to a contact pad on the external printed circuit board, and a sloped portion 4c, connecting and joining the first and second substantially flat portions 4a, 4b. 
In particular, accelerometer integrated sensors are known, including a package (e.g., of the gull-wing leaded type), encapsulating a related micromechanical sensing structure and electronic circuit.
The package is designed to be coupled, e.g., via soldering, to a printed circuit board of an electronic apparatus, e.g., a portable apparatus (such as a smartphone, a tablet, a PDA, a portable PC, a camera), or an air-bag control module of an automotive vehicle.
In several applications, the mechanical resonant frequency of the packaged semiconductor device, when mounted on the external printed circuit board, is an important design specification, affecting the performance of the overall system.
For example, in the automotive field, accelerometer sensors used for airbag applications are often desired to have a minimum natural resonant frequency of at least 45 kHz, when mounted on the external board, in order to assure reliable operation.